#related topic: I think fionna has a vibe of also taking care of her friends in her own way in the past

[paragonrobits]

today's hot take: i don't read Fionna and Simon's relationship as parental at ALL, because while their initial foreshadowing is heavily romantic in nature (Ice Prince being depicted as a Tuxedo Mask-esque handsome icon being Fionna's essential establishing character moment for Simon before she is initially annoyed by his sour attitude and then comes to know him better and then care about him), there's a few other points for them explicitly not having a father/daughter dynamic at all, but the biggest one is that they are fundamentally peers.

This might not be readily apparent because of their ages, but at the ages they're at and that inform their world view and relationships to others like them, they're pretty much in the same bracket. Fionna is in her 30s, while Simon was originally 47 when he got the crown, and nearly in his 60s at this point; while you may assume that her being almost literally half his age works against the interpretation of them having similar experiences, they ARE at the age where age differences honestly don't really mean that much and gradually become irrelevant in terms of lived experiences.

The bigger thing, though, is that their status as complementary story foils are the most relevant bit for their characters.

Fionna and Simon are foils to each other, with a nearly identical start to their character arcs: they BOTH long for a different sort of world than the one they got, but from opposite directions. Fionna lives in a mundane 9-to-5 world and wants a magical world of adventure. Simon is in that world (after living through the gradual process to make a mundane world into a magical one) but he wants the more mundane experience he remembers once, and he just can't feel that he belongs in Ooo, just as Fionna can't help but feel all wrong for her mundane world. While Simon doesn't have any interest in making Ooo boring and normal, he DOES latch on fast towards the idea of becoming Ice King again even as he clearly hates it, because he desperately fixates on the idea of being needed by others, even (no, ESPECIALLY) if it hurts him in the process.

They both want to be heroes, in their way, and resent being part of worlds that they feel they don't belong in anymore, and clearly ignore multiple opportunities to find magic or meaning in the world right around them, and SPECIFICALLY ignoring them in pretty much the same ways, to the point that the episodes Fionna Campbelll and Simon Petrikov parallel each other, not just in titles but in general progression; they go through a lot of similar circumstances, to the point of encountering the same sort of circumstances that they ignore or swat away. It's not the magic or normal they WANT... or perhaps wanting isn't even the right word. Their experiences or vague memories of the world they used to know keeps demanding to have something more like that; they ignore friends and family, or explicitly go out of their way to not tell them anything; Simon shuts down his feelings and won't tell Finn or Marceline anything (almost certainly because he feels like he would be bothering them) and while Fionna goes to her friends for help, she doesn't really confide in them.

This extends even to their songs, Not Myself and Part of The Madness; they both have very similar overtones of depression, feeling out of place, and fundamental loneliness. Its different in the particulars; Fionna is weighed down by the mundanity and changelessness of her world, feeling alone even with her friends. Simon glumly wants to help people but he CAN'T do anything without magic; no one needs anything from him, and people (he thinks) aren't happy to see him.

Fionna longs for an inexpressible time of magic and without it, she feels lost and empty. Simon wants to be needed and feels empty inside BECAUSE he thinks he's supposed to be better now, but all it does is make him feel upset and bad about being upset. Fionna's primary issue is that she's... lost, in a similar way. She remembers her world being magical but not clearly, much as the vague impressions Simon recalls his experience as Ice King; we don't even know WHAT her life has been like, and its entirely possible that everyone's life is a blurry hazy mess in the mundane world she's gotten, but she and Cake are the only ones with the awareness to work it out and be unhappy. Both Simon and Fionna can't help but remember how things used to be, or that they COULD be another way, and be endlessly lost in their own gloom and dissatisfaction.

Past the point where they actually meet and are starting to like each other's company (to the point that they remain in contact across the gulf of worlds post-minseries), these factors and their generall dynamic (Simon as a wet cat in a perpetual state of OH SHIT while Fionna tries her best to be a bruiser but unfortunately finds that in her life she doesn't have the skills or power to pull it off, leading to them BOTH feeling useless) make them both feel like peers; people with similar problems in the same boat. A lot of Fionna's character development comes from her slowly realizing what she's actually asking from Simon and her growing fear of making her world as dangerous or frightening as some of the places she's seen, while Simon has to come to terms with the fact that he really DOESN'T want to be Ice King again and that he needs to come to terms with it.

As a result of all that, they have a strong vibe of feeling like peers, not like a student and teacher or a similar dynamic.

(Also Fionna DID smooch Winter King with zero hesitation and while that didn't end well for anyone involved except PB, no one found this unusual in-universe. Except possibly Simon and HIS primary issue feels more like he thought of Winter King as a better version of himself in general and he got resentful about that.)